1. Field of the Invention
The present invention relates to a combustor for a gas turbine engine, and, more particularly, to a dome assembly for a gas turbine engine combustor which regenerates spent cooling air into the combustion process.
2. Description of Related Art
An important goal in the current design of gas turbine engine combustors is the reduction of emissions in the form of carbon monoxide, unburned hydrocarbons, and oxides of nitrogen. Fundamental to such designs is the thorough premixing of fuel and air, as well as the burning of such premixture at lean fuel/air ratios. At the same time, a certain amount of cooling air is required in order to maintain combustor liner temperatures, as well as to protect the dome of the combustor. In order to provide this required cooling, the conventional strategy has been to segregate the cooling air from the combustion air, which thereby builds in fundamental inhomogenieties in fuel/air distribution.
As seen in U.S. Pat. No. 4,180,974 to Stenger, et al., a series of heat shield plates or baffles are utilized to protect the dome structure from direct radiant heat load. These plates or baffles are conventionally cooled by a series of impinging air jets, which are formed by compressed air flowing through cooling passages in the dome. Once this cooling impingement cooling air is spent, it is then directed along the walls to augment the film cooling of the adjacent liner structure. However, the exit gaps at the edges of the baffles are typically not very well controlled, whereby utilization of the spent baffle cooling air for film cooling is not efficient and cannot be tailored to address identifiable hot spots. It will also be understood that this impingement cooling air is kept separate from combustion air mixed with fuel in the carburetor until the combustion chamber, at which point inhomgenieties with the fuel/air premixture occur resulting in increased emissions.
Accordingly, it would be desirable for a combustor dome assembly to be developed which overcomes the competing goals of lower emissions and combustor cooling caused by segregation of combustion and cooling air, especially one which may be utilized with either a single or multiple annular dome combustor.